Parametric cost models are routinely used to plan missions, compare concepts and justify technology investments. However, great care is required. Some space telescope cost models, such as those based only on mass, lack sufficient detail to support such analysis and may lead to inaccurate conclusions. Similarly, using ground based telescope models which include the dome cost will also lead to inaccurate conclusions. This paper reviews current and historical models. Then, based on data from 22 different NASA space telescopes, this paper tests those models and presents preliminary analysis of single- and multi-variable space telescope cost models.

The Joint Dark Energy Mission (JDEM)^1,2 is a proposed dark energy space mission that will measure the expansion history of the universe and the growth of its large scale structure. It is intended to provide tight constraints on the equation of state of the universe and test the validity of general relativity. Three complementary observational analyses will be employed: Baryon Acoustic Oscillations, Type 1a Supernovae and Gravitational Weak Lensing. An observatory designed for efficient accommodation of these techniques combines wide-field, diffraction-limited observations, ultra-stable point spread function, and spectroscopy. In this paper we discuss optical configurations capable of simultaneous wide-field imaging and spectroscopy, using either afocal or focal telescope configurations. Spectroscopy may be performed by an integral field unit (IFU), grism or prism spectrometer. We present a flowdown of weak lensing image stability requirements (the most demanding technique optically) to telescope thermo-mechanical stability limits, based on variations in the optical transfer function of combinations of Zernike modes, and the sensitivity of these mode combinations to thermo-mechanical drift of the telescope. We apply our formalism to a representative threemirror anastigmat telescope and find quantitative relations between the second moments of the image and the required stability of the telescope over a typical weak lensing observation.

The Euclid mission has been proposed as a powerful probe of Dark Matter and Dark Energy, using complementary space-borne imaging and spectroscopy techniques. The mission concept is being assessed as part of the European Space Agency (ESA) Cosmic Visions 2015-25 programme. The mission concept is described, including some of the critical trade-offs. The scientific performance predictions are briefly presented.

The paper provides a summary of the results of the assessment study conducted on the SPICA Telescope Assembly (STA). SPICA (SPace Infrared telescope for Cosmology and Astrophysics) was selected for study as a mission of opportunity within the science programme Cosmic Vision 2015-2025 of the European Space Agency, with a planned launch in 2017. Observing in the 5 - 210 micron waveband, one of its major goals is the discovery of the origins of planets and galaxies. ESA's main contribution is the provision of the SPICA Telescope Assembly (STA) featuring a 3.5 m primary mirror cooled to < 6K. A nationally funded European FIR instrument (SAFARI) would also be part of SPICA's payload. Following an internal ESA study carried out in Q1 and Q2 2008, a parallel competitive industrial study (phase A level) has been performed. The main results achieved during this study are summarised.

We present the results of the Astrophysics Strategic Mission Concept Study for the New Worlds Observer (NWO). We show that the use of starshades is the most effective and affordable path to mapping and understanding our neighboring planetary systems, to opening the search for life outside our solar system, while serving the needs of the greater astronomy community. A starshade-based mission can be implemented immediately with a near term program of technology demonstration.

NASA's planned Ares V cargo launch vehicle with its 10 m diameter fairing and ~60,000 kg payload mass to L2 offers the potential to launch entirely new classes of missions, such as 8-m monolithic aperture telescopes, 12- to 16-m aperture x-ray telescopes, 16- to 24-m segmented telescopes and highly capable outer planet missions. This paper summarizes the current Ares V baseline performance and reviews potential mission concepts enabled by these capabilities.

Future large UV-optical space telescopes offer new and exciting windows of scientific parameter space. These telescopes can be placed at L2 and borrow heavily from the James Webb Space Telescope (JWST) heritage. For example, they can have similar deployment schemes, hexagonal mirrors, and use Wavefront Sensing and Control (WFSC) technologies developed for JWST. However, a UV-optical telescope requires a 4x improvement in wavefront quality over JWST to be diffraction-limited at 500 nm. Achieving this tolerance would be difficult using a passive thermal architecture such as the one employed on JWST. To solve this problem, our team has developed a novel Hybrid Sensor Active Control (HSAC) architecture that provides a cost effective approach to building a segmented UV-optical space telescope. In this paper, we show the application of this architecture to the ST-2020 mission concept and summarize the technology development requirements.

ATLAST-8 is an 8-meter monolithic UV/optical/NIR space observatory to be placed in orbit at Sun-Earth L2 by NASA's planned Ares V cargo launch vehicle. ATLAST-8 will yield fundamental astronomical breakthroughs. A one year mission concept study has developed a detailed point design for the optical telescope assembly and spacecraft. The mission concept assumes two enabling technologies: NASA's planned Ares-V launch vehicle (scheduled for 2019) and autonomous rendezvous and docking (AR&D). The unprecedented Ares-V payload and mass capacity enables the use of a massive, monolithic, thin-meniscus primary mirror - similar to a VLT or Subaru. Furthermore, it enables simple robust design rules to mitigate cost, schedule and performance risk. AR&D enables on-orbit servicing, extending mission life and enhancing science return.

Stellar Imager (SI) is a space-based, UV/Optical Interferometer (UVOI) with over 200x the resolution of HST. It will enable 0.1 milli-arcsec spectral imaging of stellar surfaces and the Universe in general and open an enormous new "discovery space" for astrophysics with its combination of high angular resolution, dynamic imaging, and spectral energy resolution. SI's goal is to study the role of magnetism in the Universe and revolutionize our understanding of: 1) Solar/Stellar Magnetic Activity and their impact on Space Weather, Planetary Climates, and Life, 2) Magnetic and Accretion Processes and their roles in the Origin & Evolution of Structure and in the Transport of Matter throughout the Universe, 3) the close-in structure of Active Galactic Nuclei and their winds, and 4) Exo-Solar Planet Transits and Disks. SI is a "Landmark/Discovery Mission" in 2005 Heliophysics Roadmap and a candidate UVOI in the 2006 Astrophysics Strategic Plan and is targeted for launch in the mid-2020's. It is a NASA Vision Mission and has been recommended for further study in a 2008 NRC report on missions potentially enabled/enhanced by an Ares V launch. In this paper, we discuss the science goals and required capabilities of SI, the baseline architecture of the mission assuming launch on one or more Delta rockets, and then the potential significant enhancements to the SI science and mission architecture that would be made possible by a launch in the larger volume Ares V payload fairing, and by servicing options under consideration in the Constellation program.

Future space based telescopes will need apertures and focal lengths that exceed the dimensions of the launch vehicle shroud. In addition to deploying the primary mirror and secondary mirror support structure, these large telescopes must also deploy the stray light and thermal barriers needed to ensure proper telescope performance. The authors present a deployable light and thermal optical barrel assembly approach for a very large telescope with a variable sun angle and fast slew rate. The Strain Energy Deployable Optical Barrel Assembly (SEDOBA) uses elastic composite hinges to power the deployment of a hierarchical truss structure that supports the thermal and stray light shroud material that form the overall system. The paper describes the overall design approach, the key component technologies, and the design and preliminary testing of a self deploying scale model prototype.

This is part six of a series describing the ongoing optical modeling activities for the James Webb Space Telescope (JWST). The first two discussed modeling JWST on-orbit performance using wavefront sensitivities to predict line of sight motion induced blur and stability during thermal transients. The third investigates the aberrations resulting from alignment and figure errors after compensation of the controllable degrees of freedom of the observatory (i.e. primary and secondary mirrors). This paper follows the theme of the third, but considers the highly unlikely case where a gross figure error occurs on the secondary mirror. We then compensate for this error using figure control on the primary mirror. The level of compensation as well as the total motions required are evaluated and reported. Impact to image quality over the full field of the observatory is also discussed.

The James Webb Space Telescope (JWST) consists of an optical telescope element (OTE) that sends light to five science instruments. The initial steps for commissioning the telescope are performed with the Near-Infrared Camera (NIRCam) instrument, but low-order optical aberrations in the remaining science instruments must be determined (using phase retrieval) in order to ensure good performance across the entire field of view. These remaining instruments were designed to collect science data, and not to serve as wavefront sensors. Thus, the science cameras are not ideal phase-retrieval imagers for several reasons: they record under-sampled data and have a limited range of diversity defocus, and only one instrument has an internal, narrowband filter. To address these issues, we developed the capability of sensing these aberrations using an extension of image-based iterative-transform phase retrieval called Variable Sampling Mapping (VSM). The results show that VSM-based phase retrieval is capable of sensing low-order aberrations to a few nm RMS from images that are consistent with the non-ideal conditions expected during JWST multi-field commissioning. The algorithm is validated using data collected from the JWST Testbed Telescope (TBT).

The James Webb Space Telescope (JWST) requires testing of the full optical system in a cryogenic vacuum environment before launch. Challenges with the telescope architecture and the test environment lead to placing removable optical test sources at the Cassegrain intermediate focus of the Telescope. The Science Instrument suite will be used to align the telescope and to verify the wavefront error. The Science Instruments capture test images that are analyzed using focus diverse phase retrieval. The wavefront sensing algorithms have the large dynamic range required to measure the relatively small wavefronts of interest in the presence of the large aberrations resulting from the off-axis source locations at the intermediate focus. These inherent aberrations of the off-axis design are removed analytically from the measured data. The test design and in-situ wavefront sensing process enables a number of tests to verify the alignment and optical quality of the system.

One economically and technologically feasible bedrock structure for constructing large (diameter > 10 m) space telescopes is a segmented or sparse aperture system with subcomponents in precision formation flight. For UV/Visible/IR systems, initial targeting and targeting new objects to establish initial fringes requires the positioning precision to nm - μm accuracy, thus the control system should be capable of the required precision positioning and attitude controls without producing contaminations from thruster exhaust plumes. A nanometer accuracy contaminationfree formation architecture, Photon Tether Formation Flight (PTFF), based on Photonic Laser Thrusters (PLTs) and tethers has been proposed to exploit a force equilibrium formed by PLT thrust and tether tension for forming precision persistent 3-D formation structures ideal for the large UV/Visible/IR space telescopes. The range of the PLT force can theoretically extend over several kms. Under previous NASA sponsorship, we have successfully demonstrated a proofof- concept PLT. In addition, the demonstrations of required laser components, optics and tracking technologies developed under military laser applications now support that implementation of PLTs for large space telescopes is one step closer to reality.

The Precision Formation Control project seeks to demonstrate experimentally the capability to perform optical pathlength stabilization of a visible-laser interferometer beam operating between two formation-flying robotic airbearing space-vehicle emulators in a terrestrial laboratory environment, as a precursor to future separated-spacecraft interferometer missions. The multi-tiered architecture utilizes laser sensors for inter-vehicle sensing, proportional pneumatic thrusters for vehicular control, and a piezo-actuated delay line for optical pathlength control. In the lab environment, relative stationkeeping between vehicles has been demonstrated to better than 9 μm in position and 11 μrad in rotation (1-σ). Simultaneously, the inter-vehicle optical pathlength has been stabilized to less than 190 nm, 1-σ.

The nineteenth century Fraunhofer primary objective grating (POG) telescope has been redesigned with a secondary spectrometer. The POG is embossed on a membrane and placed at an angle of grazing exodus relative to a conventional spectrographic telescope. The result is a new type of telescope that disambiguates overlapping spectra and can capture spectral flux from all objects over its free spectral range, nearly 40°. For space deployment, the ribbon-shaped membrane can be stowed as a cylinder under a rocket fairing for launch and deployed in space from a cylindrical drum. Any length up to kilometer scale could be contemplated.

The Lunar Radio Array (LRA) is a concept for a telescope sited on the farside of the Moon with a prime mission of making precision cosmological measurements via observations of neutral hydrogen.

Lightweight, actuated, silicon carbide mirrors are an enabling technology for large aperture, space-based optical systems. These mirrors have the potential to improve optical resolution and sensitivity beyond what is currently possible. However, launch survival is a key concern, especially for very lightweight mirrors. This work uses an integrated modeling approach to determine the vibroacoustic response of mirrors subjected to launch loads through the calculation of peak launch stresses in the silicon carbide substrate and in the actuators. The fully parameterized model used with optimization and trade space exploration allows for the identification of key design parameters for launch survival. The areal density, number or ribs, rib structure, and face sheet thickness are identified as key variables that affect the launch stress and are varied in the optimization. Optimal designs, in terms of lowest peak stress and lowest mass meeting launch stress requirements, are found, and iso-performance is used to identify multiple sets of design parameters that meet launch survival requirements. This modeling effort expands the knowledge of lightweight mirrors through the determination of technology limitations imposed by the launch environment. The modeling method also allows for the addition of uncertainty analysis and launch load alleviation techniques.

The trend in future space telescopes is towards larger apertures, which provide increased sensitivity and improved angular resolution. Lightweight, segmented, rib-stiffened, actively controlled primary mirrors are an enabling technology, permitting large aperture telescopes to meet the mass and volume restrictions imposed by launch vehicles. Such mirrors, however, are limited in the extent to which their discrete surface-parallel electrostrictive actuators can command global prescription changes. Inevitably some amount of high spatial frequency residual error is added to the wavefront due to the discrete nature of the actuators. A parameterized finite element mirror model is used to simulate this phenomenon and determine designs that mitigate high spatial frequency residual errors in the mirror surface figure. Two predominant residual components are considered: dimpling induced by embedded actuators and print-through induced by facesheet polishing. A gradient descent algorithm is combined with the parameterized mirror model to allow rapid trade space navigation and optimization of the mirror design, yielding advanced design heuristics formulated in terms of minimum machinable rib thickness. These relationships produce mirrors that satisfy manufacturing constraints and minimize uncorrectable high spatial frequency error.

Presented is a novel optical system using Cis-Trans photoisomerization where nearly every molecule of a mirror substrate is itself an optically powered actuator. Primary mirrors require sub-wavelength figure (shape) error in order to achieve acceptable Strehl ratios. Traditional telescopy methods require rigid and therefore heavy mirrors and reaction structures as well as proportionally heavy and expensive spacecraft busses and launch vehicles. Areal density can be reduced by increasing actuation density. Making every molecule of a substrate an actuator approaches the limit of the areal density vs actuation design trade space. Cis-Trans photoisomerization, a reversible reorganization of molecular structure induced by light, causes a change in the shape and volume of azobenzene based molecules. Induced strain in these "photonic muscles" can be over 40%. Forces are pico-newtons/molecule. Although this molecular limit is not typically multiplied in aggregate materials we have made, considering the large number of molecules in a mole, future optimized systems may approach this limit In some π-π* mixed valence azo-polymer membranes we have made photoisomerization causes a highly controllable change in macroscopic dimension with application of light. Using different wavelengths and polarizations provides the capability to actively reversibly and remotely control membrane mirror shape and dynamics using low power lasers, instead of bulky actuators and wires, thus allowing the substitution of optically induced control for rigidity and mass. Areal densities of our photonic muscle mirrors are approximately 100 g/m2. This includes the substrate and actuators (which are of course the same). These materials are thin and flexible (similar to saran wrap) so high packing ratios are possible, suggesting the possibility of deployable JWST size mirrors weighing 6 kilograms, and the possibility of ultralightweight space telescopes the size of a football field. Photons weigh nothing. Why must even small space telescopes weigh tons? Perhaps they do not.

The benefits Astronomy could gain by performing multi-slit spectroscopy in a space mission is renown. Digital Micromirror Devices (DMD), developed for consumer applications, represent a potentially powerful solution. They are currently studied in the context of the EUCLID project. EUCLID is a mission dedicated to the study of Dark Energy developed under the ESA Cosmic Vision programme. EUCLID is designed with 3 instruments on-board: a Visual Imager, an Infrared Imager and an Infrared Multi-Object Spectrograph (ENIS). ENIS is focused on the study of Baryonic Acoustic Oscillations as the main probe, based on low-resolution spectroscopic observations of a very large number of high-z galaxies, covering a large fraction of the whole sky. To cope with these challenging requirements, a highmultiplexing spectrograph, coupled with a relatively small telescope (1.2m diameter) has been designed. Although the current baseline is to perform slit-less spectroscopy, an important option to increase multiplexing rates is to use DMDs as electronic reconfigurable slit masks. A Texas Instrument 2048x1080 Cinema DMD has been selected, and space validation studies started, as a joint ESA-ENIS Consortium effort. Around DMD, a number of suited optical systems has been developed to project sky sources onto the DMD surface and then, to disperse light onto IR arrays. A detailed study started, both at system and subsystem level, to validate the initial proposal. Here, main results are shown, making clear that the use of DMD devices has great potential in Astronomical Instrumentation.

A key consideration in designing optical systems, instruments, or test setups requiring windows or beam combiners is the potential for ghost images to be produced from reflections off the window/combiner surfaces. These ghost images will affect the optical system performance and the level to which that performance can be demonstrated during verification testing. Two common solutions for this are to use anti-reflection coatings and to use wedged substrates. Each has performance implications when used in spectrally broadband systems. The use of coatings alone on windows/combiners results in modest reduction (<100X) of ghost image intensity that can be inadequate when using or testing systems designed to find weak targets near bright objects. Using wedged substrates to shift ghost images outside an image region of interest will introduce chromatic aberrations that limit the fundamental broadband system imaging performance. In this paper we present design parameters for window/combiner assemblies that shift ghost images from a region of interest while controlling the chromatic aberrations to a level whereby the system imaging performance is not adversely affected even for broadband imaging systems with high angular resolution. We then present an example demonstrating the performance of a typical low dispersion, ghost-controlled window/combiner assembly.

Space-borne large optics will be required in future missions for astronomy and earth observations. In order to realize large-optics missions, JAXA has started the study of the ground measurement techniques of large optics. The 6m diameter radiometer thermal vacuum chamber (6m chamber) at Tsukuba Space Center will be used for tests of JAXA's future large-optics missions like Space Infrared Telescope for Cosmology and Astrophysics (SPICA). We measured the vibration environment of the 6m chamber for the feasibility study of precise optical measurement. We placed a test mirror inside the chamber and measured the surface figures of the mirror from outside the chamber with a high-speed interferometer, while the chamber was being vacuum-pumped and cooled by liquid nitrogen; we also directly measured the vibrational levels with accelerometers concurrently. The measurements were performed for each phase of the chamber system operation including pumping and cooling processes. This paper presents the results about optical measurement under the vibration environment on the 6m chamber. We confirm that the vibrations from pumps and shroud have negligible effects on optical measurements owing to a vibration isolation system in the 6m chamber.

The Kepler spacecraft and telescope were designed, built and tested at Ball Aerospace & Technologies Corporation in Boulder, Colorado. The Kepler spacecraft was successfully launched from NASA's Kennedy Space Center on March 6, 2009. In order to adequately support the Kepler mission, Ball Aerospace upgraded its optical testing capabilities. This upgrade facilitated the development of a meter-class optical testing capability in a thermal vacuum (TVAC) environment. This testing facility, known as the Vertical Collimator Assembly (VCA), was used to test the Kepler telescope in 2008. Ball Aerospace designed and built the VCA as a 1.5m, f/4.5 collimator that is an un-obscured system, incorporating an off-axis parabola (OAP) and test flat coated for operations in the VIS-IR wavelength region. The VCA is operated in a large thermal vacuum chamber and has an operational testing range of 80 to 300K (-315 to 80°F). For Kepler testing, the VCA produced a 112nm rms wavefront at cryogenic temperatures. Its integral autocollimation and alignment capabilities allowed knowledge of the collimated wavefront characteristics to <5nm rms during final thermal vacuum testing. Upcoming modifications to the VCA optics will bring the VCA wavefront to <20nm rms. The VCA optics are designed and mounted to allow for use in either a vertical or horizontal orientation without degradation of the collimated optical wavefront.

Advanced astronomical missions with greatly enhanced resolution and physics missions of unprecedented accuracy will require a spaceworthy laser distance gauge of substantially improved performance. The Tracking Frequency Gauge (TFG) uses a single beam, locking a laser to the measurement interferometer. We have demonstrated this technique with pm (10^-12 m) performance. We report on the version we are now developing based on space-qualifiable, fiber-coupled distributed-feedback semiconductor lasers..